1. Field of the Invention
The present invention relates generally to a technical field of vehicular velocity controlling system and method for an automotive vehicle (host vehicle) to control a vehicular velocity of the host vehicle to become substantially equal to a set vehicular velocity set by a vehicular driver.
2. Description of the Related Art
Various types of vehicular velocity controlling systems have been proposed, in which the vehicular velocity is merely controlled so that the vehicular velocity is made substantially equal to a set vehicular velocity that the vehicle driver has set and in which the vehicle is running in accordance with the set vehicular velocity in an event where a preceding vehicle which is running ahead of the vehicle is not present and the inter-vehicle distance is detected and the vehicular velocity of the host vehicle is controlled in a predetermined vehicular velocity range lower than the driver""s set vehicular velocity (hereinafter, also called a set vehicular velocity) in accordance with a detected inter-vehicle distance and/or relative velocity to the preceding vehicle where the preceding vehicle is present.
A Japanese Patent Application First Publication No. Heisei 9-286257 published on Nov. 4, 1997 exemplifies a previously proposed inter-vehicle distance controlling system in which with the vehicular velocity controlling system of a preceding vehicle follow-up type as a prerequisite, the vehicular velocity when the preceding vehicle was placed at the position of the host vehicle is referred to and the vehicular velocity is implemented with the vehicular velocity as an upper limit value thereof.
In the previously proposed inter-vehicle distance controlling system disclosed in the above-described Japanese Patent Application First Publication, a road surface frictional coefficient is detected.
If the road surface frictional coefficient is small, namely, if the vehicle is running on a low frictional coefficient (xcexc) road surface, the referenced vehicular velocity is applied as an upper limit value.
As described above, the vehicular velocity of the preceding vehicle by which the host vehicle is followed is set to the upper limit value of the vehicular velocity when the vehicle has arrived at the position. If a vehicle driver of the preceding vehicle has decelerated the preceding vehicle due to some reason, the host vehicle is also decelerated according to the deceleration of the preceding vehicle.
It becomes possible to reduce the vehicular velocity in response to some phenomenon that would be recognizable from the host vehicle so that a running stability would be improved.
However, in such previously proposed vehicular velocity controlling systems as described above in which the vehicular velocity is merely controlled to become substantially equal to the set vehicular velocity, the vehicular velocity is controlled in accordance with the set vehicular velocity of a vehicular driver irrespective of a vehicular running state. In addition, in the other previously proposed vehicular velocity controlling systems in which the vehicular velocity is controlled in accordance with the set vehicular velocity of a vehicular driver irrespective of a vehicular running state.
In addition, in the other previously proposed vehicular velocity controlling system in which the vehicular velocity is controlled with the inter-vehicle distance and relative velocity of the host vehicle to the preceding vehicle taken into consideration, the vehicular velocity is controlled in accordance with the set vehicular velocity by the vehicular driver in the same way as described in the former case when the distance to the preceding vehicle is sufficient and when the preceding vehicle is running at a sufficiently high velocity so that the vehicular velocity is controlled at a velocity value which accords with the set vehicular velocity by the driver and irrespective of a running state except the preceding vehicle.
Therefore, even if, for example, the vehicle is running on a low road surface having a low frictional coefficient, it is possible to set an arbitrarily high set vehicular velocity. In addition, in a case where the control such that the vehicular velocity of the preceding vehicle by which the host vehicle is followed is set to the upper limit value of the vehicular velocity of the host vehicle is carried out, such a situation that the preceding vehicle is present, a vehicle driver takes an attention to a state of the road surface and operates for the preceding vehicle to be decelerated to cope with the low frictional coefficient of the road surface.
In this case, there is a possibility of improving the running stability since the vehicle is also decelerated. However, if the vehicle driver of the preceding vehicle does not take the attention to the low frictional coefficient of the road surface on which the preceding vehicle is running and the vehicle driver of the preceding vehicle does not decelerate the preceding vehicle, the host vehicle would not be decelerated.
That is to say, there is a task to be solved such that the vehicular velocity of the host vehicle is controlled dependently on the preceding vehicle.
It is, hence, an object of the present invention to provide vehicular velocity controlling system and method for an automotive vehicle in which the host vehicle is running with its vehicular velocity suppressed to be lowered irrespective of the vehicular velocity of the preceding vehicle when the vehicle is running on the low frictional coefficient road surface, an improvement of the vehicular running stability independently of the preceding vehicle is made, and a sense of security of the host vehicle driver can be achieved.
The above-described object can be achieved by providing a vehicular velocity controlling system comprising: a vehicular velocity detector to detect a vehicular velocity; an inter-vehicle distance detector to detect an inter-vehicle distance from a vehicle to a preceding vehicle which is running ahead of the vehicle; a manual vehicular velocity setting section enabled to manually set a set vehicular velocity; a vehicular velocity controller to perform a vehicular velocity control in such a manner that the inter-vehicle distance is substantially made equal to a target inter-vehicle distance set on the basis of at least the vehicular velocity during a presence of the preceding vehicle detected by the inter-vehicle distance detector and in such a manner that the vehicular velocity is substantially made equal to the set vehicular velocity through the manual vehicular velocity setting section during an absence of the preceding vehicle; a road surface frictional coefficient detector to detect a road surface frictional coefficient of a road surface; and an upper limit vehicular velocity setting section that sets an upper limit value of the vehicular velocity for the vehicular velocity control in accordance with the detected road surface frictional coefficient, below the upper limit value of which the vehicular velocity controller is enabled to perform the vehicular velocity control, in such a manner that as the road surface frictional coefficient becomes lower, the upper limit value becomes lower.
The above-described object can also be achieved by providing a vehicular velocity controlling system comprising: a vehicular velocity detector to detect a vehicular velocity; a manual vehicular velocity setting section enabled to manually set a set vehicular velocity; a vehicular velocity controller to perform a vehicular velocity control in such a manner that the vehicular velocity is substantially made equal to the set vehicular velocity by the manual vehicular velocity setting section; a road surface frictional coefficient detector to detect a road surface frictional coefficient of a road surface; and an upper limit vehicular velocity setting section that sets an upper limit value of the vehicular velocity in accordance with the detected road surface frictional coefficient, below the upper limit value of which the vehicular velocity controller is enabled to perform the vehicular velocity control, in such a manner that as the road surface frictional coefficient becomes lower, the upper limit value of the vehicular velocity control becomes lower.
The above-described object can also be achieved by providing a vehicular velocity controlling method comprising: detecting a vehicular velocity; detecting an inter-vehicle distance from a vehicle to a preceding vehicle which is running ahead of the vehicle; manually set a set vehicular velocity; performing a vehicular velocity control in such a manner that the inter-vehicle distance is substantially made equal to a target inter-vehicle distance set on the basis of at least the vehicular velocity during a presence of the preceding vehicle; performing the vehicular velocity control in such a manner that the vehicular velocity is substantially made equal to the set vehicular velocity an absence of the preceding vehicle; detecting a road surface frictional coefficient of a road surface; and setting an upper limit value of the vehicular velocity for the vehicular velocity control in accordance with the detected road surface frictional coefficient, below the upper limit value of which the vehicular velocity control is enabled to be performed, in such a manner that as the road surface frictional coefficient becomes lower, the upper limit value becomes lower.
The above-described object can also be achieved by providing a vehicular velocity controlling method comprising: detecting a vehicular velocity; manually setting a set vehicular velocity; performing a vehicular velocity control in such a manner that the vehicular velocity is substantially made equal to the set vehicular velocity; detecting a road surface frictional coefficient of a road surface; and setting an upper limit value of the vehicular velocity in accordance with the detected road surface frictional coefficient, below the upper limit value of which the vehicular velocity control is enabled to be performed, in such a manner that as the road surface frictional coefficient becomes lower, the upper limit value of the vehicular velocity control becomes lower.
The above-described object can also be achieved by providing a vehicular velocity controlling system comprising: vehicular velocity detecting means for detecting a vehicular velocity; inter-vehicle distance detecting means for detecting an inter-vehicle distance from a vehicle to a preceding vehicle which is running ahead of the vehicle; manual vehicular velocity setting means for manually setting a set vehicular velocity; vehicular velocity controlling means for performing a vehicular velocity control in such a manner that the inter-vehicle distance is substantially made equal to a target inter-vehicle distance set on the basis of at least the vehicular velocity during a presence of the preceding vehicle detected by the inter-vehicle distance detecting means and in such a manner that the vehicular velocity is substantially made equal to the set vehicular velocity through the manual vehicular velocity setting means during an absence of the preceding vehicle; road surface frictional coefficient detecting means for detecting a road surface frictional coefficient of a road surface; and upper limit vehicular velocity setting means for setting an upper limit value of the vehicular velocity for the vehicular velocity control in accordance with the detected road surface frictional coefficient, below the upper limit value of which the vehicular velocity controlling means is enabled to perform the vehicular velocity control, in such a manner that as the road surface frictional coefficient becomes lower, the upper limit value becomes lower.